Estimation of evapotranspiration and its components from an apple orchard in northwest China using sap flow and water balance methods

Abstract

Abstract:Field experiments were conducted to investigate the effects of leaf area index and soil moisture content on evapotranspiration and its components within an apple orchard in northwest China for 2 years. Evapotranspiration in the non-rainfall period was estimated using two approaches: the soil water balance method based on tube-type time-domain reflection measurements, and sap flow plus micro-lysimeter methods. The two methods were in good agreement, with differences usually less than 10%. The components of evapotranspiration varied with canopy development. During spring and autumn, soil evaporation was dominating as result of low leaf area index. In summer, plant transpiration became significant, with an average transpiration to evapotranspiration ratio of 0Ð87. The crop coefficient K c showed a strong linear dependence on leaf area index. The water stress coefficient K s was around 1Ð0 when soil moisture was above 23% and started to decrease linearly after that. This study demonstrates that prediction of evapotranspiration in apple orchards can be made using the Food and Agriculture Organization's crop coefficient method from commonly available meteorological data in the area.

Canopy interception of apple orchards should not be ignored when assessing evapotranspiration partitioning on the Loess Plateau in China

“…Gong et al () and Gong et al () measured transpiration and soil evaporation in apple orchards using sap flow and micro‐lysimeter methods, respectively, and found that sums of these measurements agreed well with estimates of ET obtained using the soil water balance method. In the two cited studies, ET values obtained using the soil water balance method were used as standards to assess the results of ET measurements by the sap flow and microlysimeter methods.…”

Estimation of regional evapotranspiration over the Southern Great Plains based on Penman-Monteith theory and the soil moisture estimates

“…A key assumption of the T s -F v method is that λE is negatively correlated with temperature [2]. The dependence of λE on T s (or changes in Ts) is complicated because a series of processes are mixed together, i.e., the cooling effect of λE, thermal inertia changing with vegetation, soil moisture and soil texture, and impact of soil moisture, Ta and available energy on λE [26,27]. It is not surprise that Penman-Monteith algorithm, a robust physical theory, have a well performance.…”

“…The ratio of transpiration to total ET depends on vegetation coverage, surface wetness, and the availability of soil water for vegetation root transpiration uptake. When the surface is wet and vegetation coverage is low, soil evaporation tends to dominate [26]. The SGP is mainly covered by cropland and grassland ( Table 1).…”

Demanda hídrica e coeficientes de cultura (Kc) para macieiras em Vacaria, RS

“…Embora existam dados de Kc para macieiras na literatura (ALLEN et al, 2006;GONG et al, 2007), nem sempre esses valores publicados se ajustam às condições locais (DRAGONI et al, 2004 Para o monitoramento hídrico do solo, foram empregados tensiômetros de punção instalados em duas profundidades, 10 e 30cm, entre três pares de plantas, correspondendo às camadas de 0 a 20cm e de 20 a 40cm, respectivamente. O intervalo de 0 a 40cm é onde se concentra a maior parte do sistema radicular da cultura (GREEN & CLOTHIER, 1999;HOFFMANN & BERNARDI, 2004), correspondendo à profundidade efetiva (PE) das raízes, que é o valor empregado nos cálculos de dimensionamento e manejo da irrigação.…”

“…Os menores valores de ETc foram registrados no início e no final do ciclo da cultura (Figura 1), correspondendo aos períodos de início de crescimento dos frutos e início da hibernação, respectivamente. GONG et al (2007) registraram, na China, valor médio de ETc, igual a 2,2mm dia -1 , com um máximo de 4,4mm dia -1 , próximos aos observados no presente trabalho. GARCÍA-PETILLO et al (2003) Figura 2 -Coeficiente de cultura (Kc) para macieira cv.…”